Newsgroups: alt.sci.planetary,alt.astronomy,sci.geo.geology
From: henry@spsystems.net (Henry Spencer)
Subject: Re: Chemists Find Tagish Lake Meteorite In A Class By Itself
Date: Sun, 10 Sep 2000 04:57:22 GMT
In article <Ffau5.20711$gg.5869947@typhoon.southeast.rr.com>,
Robert Brown <rbrown@ec.rr.com> wrote:
>...I've always
>thought it fairly remarkable that Hawaii's current location was near the
>center of the circle of oceanic tektite deposits about 65 million years ago.
It's an interesting point, but alas, Hawaii's origin is well understood.
If you look at a good map, especially one that shows underwater features
as well as surface ones, you can see the long trail of eroded earlier
versions of Hawaii left behind as the Pacific tectonic plate has moved
over a hot spot in the Earth's mantle (including the place where the
plate's motion changed abruptly, leaving a bend in the trail). Even if
you limit your attention to the existing islands, they get smaller and
quieter and more eroded as you move to the northwest, and most of the
current volcanic activity is at the southeast end.
(Nor is this unique. A number of other such hot spots are known. For
example, there is one under Yellowstone Park, and a trail of progressively
older volcanic features runs west from there.)
--
Microsoft shouldn't be broken up. | Henry Spencer henry@spsystems.net
It should be shut down. -- Phil Agre | (aka henry@zoo.toronto.edu)